Share PythonUtil.java between bootstraps

Note we're using `addLibraryIfExists()` for libraries that are needed
by the `sdl2` bootstrap, but may not be compiled on other bootstraps.
This way it should fail gracefully while letting us share 100% of the code.

Author: AndreMiras

pythonforandroid/bootstraps/common/build/src/main/java/org/kivy/android/PythonUtil.java

@@ -33,8 +33,13 @@ protected static ArrayList<String> getLibraries(File libsDir) {
         ArrayList<String> libsList = new ArrayList<String>();
         addLibraryIfExists(libsList, "sqlite3", libsDir);
         addLibraryIfExists(libsList, "ffi", libsDir);
+        addLibraryIfExists(libsList, "png16", libsDir);
         addLibraryIfExists(libsList, "ssl.*", libsDir);
         addLibraryIfExists(libsList, "crypto.*", libsDir);
+        addLibraryIfExists(libsList, "SDL2", libsDir);
+        addLibraryIfExists(libsList, "SDL2_image", libsDir);
+        addLibraryIfExists(libsList, "SDL2_mixer", libsDir);
+        addLibraryIfExists(libsList, "SDL2_ttf", libsDir);
         libsList.add("python3.5m");
         libsList.add("python3.6m");
         libsList.add("python3.7m");
@@ -70,5 +75,5 @@ public static void loadLibraries(File filesDir, File libsDir) {
         }
 
         Log.v(TAG, "Loaded everything!");
-	}
+    }
 }